Oxycarbonates in the Y(O/CO sub 3 )-Ba(O/CO sub 3 )-Cu(O/CO sub 3 ) system

Journal Article · Tue Oct 01 04:00:00 EDT 1991 · Journal of Solid State Chemistry; (United States)

DOI:https://doi.org/10.1016/0022-4596(91)90195-N· OSTI ID:7266681

Karen, P; Kjekshus, A ^[1]

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1. Univ. of Oslo (Norway)

The Ba-rich oxides in the Y(O)-Ba(O)-Cu(O) system have a high affinity toward CO{sub 2}, which is manifested in the formation of oxycarbonates. The pseudoternary system Y(O/CO{sub 3})-Ba(O/CO{sub 3})-Cu(O/CO{sub 3}) is investigated at temperatures between 780 and 1,000C in atmospheres containing oxygen and {approximately}5, {approximately}40, and {approximately}350 ppm CO{sub 2}. Three oxycarbonates are identified: (1) Tetragonal Y{sub 2}Ba{sub 3} (CO{sub 3}){sub u}O{sub 6{minus}u}, u {approx} 1, with a = 438.63(4) and c = 1185.9(2) pm. (2) Y{sub 1+x}Ba{sub 8}Cu{sub 4+z}(CO{sub 3}){sub u}O{sub 11+w}, u {approx} 2, x {element of} (0, 0.3), z {element of} (0, 0.4), and w {element of} (0.05(2), 1.08(2)) for x = z = 0. Its structure, which accommodates vacancies on both cationic and anionic sites, is closely related to (the hypothetic perovskite) BaCuO{sub 3} and represents the actual composition for the so-called 'other perovskite phase' claimed for the Y(O)-Ba(O)-Cu(O) system. (3) Tetragonal YBa{sub 2}Cu{sub 3}(CO{sub 3}){sub u}O{sub 7{minus}u{minus}{upsilon}} with a = 387.38(3) and c = 1161.2(4) pm for u {approx} 0.2, {upsilon} {approx} 0.1, when carbonate-saturated at 800C and oxygen-saturated at 320C in an {approximately}40 ppm CO{sub 2} containing oxygen atmosphere. Structurally, this oxycarbonate is derived from YBa{sub 2}Cu{sub 3}O{sub 7} by replacement of some oxygens by carbonate groups, and this phase represents the actual composition of the so-called 'high-oxygen tetragonal 123 phase,' which is nonsuperconducting down to 4 K. The thermal stability of the oxycarbonates in oxygen with p{sub CO{sub 2}} {approx} 4 Pa decreases with decreasing Ba content from 960C for (1) to 940C for (2) and to 830C for (3).

• OSTI ID: 7266681
• Journal Information: Journal of Solid State Chemistry; (United States), Journal Name: Journal of Solid State Chemistry; (United States) Vol. 94:2; ISSN 0022-4596; ISSN JSSCB
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360202* -- Ceramics
Cermets
& Refractories-- Structure & Phase Studies
ALKALINE EARTH METAL COMPOUNDS
BARIUM CARBONATES
BARIUM COMPOUNDS
BARIUM OXIDES
CARBON COMPOUNDS
CARBON DIOXIDE
CARBON OXIDES
CARBONATES
CHALCOGENIDES
CHEMICAL ANALYSIS
CHEMICAL PREPARATION
CHEMICAL PROPERTIES
COHERENT SCATTERING
COPPER CARBONATES
COPPER COMPOUNDS
COPPER OXIDES
CRYSTAL LATTICES
CRYSTAL STRUCTURE
DIFFRACTION
HOLES
HYDROGEN COMPOUNDS
INORGANIC ACIDS
LEWIS ACIDS
MOLECULAR STRUCTURE
ORTHORHOMBIC LATTICES
OXIDES
OXYGEN COMPOUNDS
PHASE STUDIES
QUANTITATIVE CHEMICAL ANALYSIS
SCATTERING
STRUCTURAL CHEMICAL ANALYSIS
SUPERCONDUCTORS
SYNTHESIS
TETRAGONAL LATTICES
TRANSITION ELEMENT COMPOUNDS
X-RAY DIFFRACTION
YTTRIUM CARBONATES
YTTRIUM COMPOUNDS
YTTRIUM OXIDES